Ultimate Guide to Rainwater Harvesting

Ultimate Guide to Rainwater Harvesting: How to Collect, Store, and Use Rainwater Safely

Rainwater harvesting is an excellent way to collect and store water for various uses, from irrigation to drinking. It is a cost-effective way to conserve water and reduce your reliance on municipal water supplies. By collecting and storing rainwater, you can use it for various non-potable purposes around your home and garden or for drinking water if the collected water is properly treated. Here’s a comprehensive guide on how to get started with rainwater harvesting.

Why Should You Harvest Rainwater?

Rainwater harvesting offers numerous benefits:

It’s free and readily available
Rainwater is excellent for plants, being free of chlorine and other chemicals
It reduces the demand on municipal water supplies
It can lower your water bills
It helps prevent stormwater runoff and associated pollution

Essential Components for a Rainwater Harvesting System

A basic rainwater harvesting system consists of these main components:

Catchment Area – usually your roof.
Gutter and Gutter Guard – to collect and channel rainwater while keeping debris out.
Downspout, Downspout Diverter, and First-Flush Diverter – to direct water into the storage system and ensure cleaner water collection.
Rain Barrel, Storage Tank, or Cistern – for storing the collected water.
Outlet – for using the collected water.
Additional Considerations – overflow plan and materials to manage excess water.

Cisterns require a few additional components: an inlet filter, outlet pipe, and pump.

How to Calculate Your Rainwater Harvesting Potential

To determine how much rainwater you can collect, use this simple formula:

1 inch of rain x 1 square foot of roof = 0.623 gallons of water.
For example, if you have a 2,000-square-foot roof and receive 1 inch of rain, you could potentially collect over 1,000 gallons of water.

Best Methods for Collecting Rainwater

Rain Barrel with Spigot

Rain barrels are the simplest and most common method for small-scale rainwater harvesting, typically providing between 50 to 100 gallons of water. They are easy to set up, affordable, and suitable for small spaces. However, it’s important to note that they can overflow during heavy rains, so consider installing an overflow system to manage excess water.

Water Tank

If you are looking to collect and store larger volumes of water, a water tank is a great option. It can be connected to multiple downspouts that can be collected from various parts of a roof. Water tanks come in various sizes and can store hundreds to thousands of gallons of water. These units cost more and require more space but if you have the money, it’s well worth the investment.

Cistern

Cisterns, whether installed above or below ground, are designed for large-scale rainwater collection and storage in the thousands of gallons. These systems are ideal for irrigation, household use, or as an emergency water source. Depending on your available space and needs, you can choose an above-ground or underground cistern.

Setting Up Your Rainwater Collection System

Here are 8 common steps to take in setting up your rainwater system.

#1 Assess Your Roof and Gutter System

The first step in building a rainwater harvesting system is to evaluate your roof and gutters:

Roof Materials – ensure that your roof is made from rain-harvesting-safe materials such as metal or tile. Avoid roofs made of treated wood or asphalt shingles, as they may leach harmful substances.
Gutter Condition – check that your gutters are clean, intact, and properly sloped to funnel water effectively. Clean out any debris that may block water flow.

#2 Choose a Collection Point

Where would you like to place your rainwater collection system?
Do you have an area where water naturally flows from your roof?

#3 Choose your storage container

Your container of choice should be food-grade and UV-resistant to ensure water quality.
If using a barrel:
- avoid one that has previously held petroleum products or soaps.
- elevate it on a sturdy platform to enhance water flow and make it easier to access.

#4 Installing your container

Position your container directly below your chosen collection point
Use a downspout diverter that will direct water from your gutters into your collection system.
Attach a gutter guard – this helps prevent debris from entering your collection system.

#5 Add a Fine-Mesh Screen to Block Contaminants

To keep your collected rainwater clean install a fine-mesh screen over the barrel opening to block leaves, insects, and other debris from entering the system. This will help maintain the quality of your stored water.

#6 Attach a Spigot and Overflow Valve

To facilitate the use of your collected rainwater:

Install a spigot at the bottom of the barrel for easy access to water.
Add an overflow valve at the top of the barrel to divert excess water when the barrel is full, preventing overflow and potential damage.

#7 Consider Additional Components for optimal performance

First-Flush Diverter – install a first-flush diverter to prevent the initial rainwater, which may contain contaminants, from entering your system.
Multiple Barrels – use connectors to link multiple barrels together for increased storage capacity.
Pump: for larger systems or to increase water pressure, you may need a pump to distribute the water.

#8 Plan for over-flow issues

Ensure that any overflow from your system is directed away from your home’s foundation to avoid potential water damage. Here are some options:

Use a flexible hose or pipe to divert excess water to a safe distance.
Install a secondary barrel or tank – you can even use a connector kit to link multiple barrels.
Install a soakaway pit or dry well in your yard to absorb overflow water into the ground.
Use an overflow diverter to channel excess water into garden beds, lawns, or other planted areas that can benefit from extra water.
Install a French drain to guide water away from the collection system and disperse it safely across your yard.
Consider creating a rain garden—a shallow, landscaped area designed to absorb and filter excess rainwater.

How to Store and Filter Rainwater for Long-Term Use

Proper filtration and storage of harvested rainwater are crucial for maintaining its quality.

Storing Harvested Water

Ideal Storage Conditions: Store water in dark, cool places to prevent algae growth. Keeping barrels covered will also reduce evaporation and keep out contaminants.
For long-term water storage, treat your harvested rainwater with a water preserver or unscented, plain household bleach (8 drops or 1/8 tsp per gallon) to prevent microbial growth. Ensure the bleach is free from dyes or added fragrances, which can contaminate the water.

Learn more about using water preservers

Filtering Rainwater

Pre-filter – use a pre-filter at the gutter or barrel inlet to catch debris before the water enters the tank.
High-Quality Filters – for potable use, filter the water through a high-quality water filter that removes bacteria, viruses, and sediment (such as Berkey or ceramic filters).

Purifying Rainwater

Additional Safety Measures – consider boiling or chemically treating the water before drinking.

Learn more about water purification methods

Maintaining Your Rainwater Harvesting System for Optimal Performance

Like anything else, the more you care for your rainwater harvesting system, the longer it will work for you to provide usable non-potable water.

Regular Cleaning: Clean your gutters and rainwater collection system regularly to avoid blockages and contamination.
Inspection: Frequently inspect barrels and filters to ensure they are functioning correctly and haven’t been compromised.
Use collected water regularly to prevent stagnation.

Practical Uses for Harvested Rainwater

Collected rainwater is ideal for:

Drinking – ONLY with proper purification
Watering gardens and lawns
Washing cars
Flushing toilets
Filling birdbaths or water features
Supplementing pools and spas

Understanding Local Laws on Rainwater Harvesting

Before you begin constructing your rainwater harvesting system, it’s crucial to research local regulations. Some areas may have restrictions or permit requirements for collecting rainwater, while others may have guidelines on how the water can be used, whether for irrigation, household use, or drinking. Visit your state’s Department of Natural Resources, Department of Environmental Quality, or a similar agency responsible for water management to find state-specific regulations on rainwater harvesting.

Conclusion: Getting Started with Your Rainwater Harvesting System

Building a rainwater harvesting system is not only an environmentally friendly option but also a smart way to ensure a reliable water supply for emergency drinking and non-potable uses, like watering your garden or washing your car. Whether you start with a simple rain barrel or invest in a larger tank or cistern system, rainwater harvesting can be tailored to fit your space and budget. Ready to take the next step in your water-saving journey? Start small by setting up a rain barrel or explore larger-scale solutions.